1. Field of the Invention
The invention relates to a locking apparatus for securing a second apparatus carried thereon to a subterranean well conduit.
2. Description of the Prior Art
During the drilling, completion, testing, production or workover of a subterranean well, it is often desirable to removably attach tools, such as valves, to the bottom of a tubing string already in place. Thus, when it is necessary to retrieve the tool for replacement or redressing, it may be retrieved by known wire line or work string, without the need to raise the entire tubing string. The tool and an associated releasable lock are lowered through the well conduit (such as casing or tubing) and locked into a locking nipple or annular landing groove formed on the interior surface of the conduit.
Prior art locks have employed outwardly expandable locking segments adapted to engage a groove formed on the inside diameter of a section of tubing. In known locks, an annular locking plunger is axially shifted to a position radially inward of the locking segments to prevent their retraction. Typically, the annular locking plunger has an upwardly and inwardly tapering conical surface, adapted to cam the locking segments into engagement with the annular landing groove as the plunger moves upwardly. There is thus a radial compressive force on the annular plunger as it cams the locking segments into locking position and retains them. To incorporate adequate strength in such units, it is necessary that the plunger be of significant thickness. It is desirable, however, that the thickness of the plunger and the locking segments be minimized to allow other tools, such as plugs, or the like, to be run through the bore of the plunger, and to minimize restriction of the fluid flow path through the plunger.